466 METABOLISM, NUTRITION, AND DIET 



could not have produced over 17 pounds. Summarized, this experiment 

 shows conclusively that fat is synthesized from carbohydrate. It requires 

 about 2 . 7 grams of dextrose to form i gram of fat, and this condensation 

 takes place with the formation of carbon dioxide and water and the libera- 

 tion of about 1 5 per cent, of the available heat of oxidation. 



Persistent excess of carbohydrate food produces an accumulation of fat, 

 which may not only be an inconvenience causing obesity, but may interfere 

 with the proper nutrition of muscles, produce a feebleness of the action of 

 the heart, and other troubles. 



The formation of fat from protein is discussed on page 459. 



Fat Mobilization in the Body. Increasing numbers of recent studies are 

 throwing new light on the phenomenon of mobilization of fat in the body. 

 In 1900 Kastle and Loevenhart discovered the reversible action of lipase 

 which opened the door to a more fitting conception of how the body is enabled 

 to handle this ordinarily insoluble constituent. Just as fats must be dis- 

 sociated in order to be absorbed, a step that converts the insoluble fat to a 

 soluble form, so the body transference from one tissue to another, from 

 the storehouse of fats to the lymph and blood, or vice versa, requires that the 

 fats must be in a soluble form, i.e., dissociated. The facility with which 

 fats can be mobilized depends upon the presence and activity of fat Upases. 

 These have been shown to be present in practically all tissues of the body, 

 greater in some, as in the liver, certain glands, etc. Under the influence of 

 the enzyme a fairly constant concentration of fats is normally present in 

 the blood and in the body fluids, and is always available as a source of 

 energy to the oxidizing tissues. The above is the explanation of the 

 increase of fat in the milk previously referred to. When no food is com- 

 ing, the animal draws immediately on the carbohydrates which are always 

 present in the blood. This store is rapidly exhausted. As tissue hunger 

 approaches, an increase in lipase production undoubtedly takes place, and 

 this dissolves and sets in motion storage fat. Under these conditions the 

 amount of fat in circulation rapidly increases and becomes available to the 

 muscles, glands, etc., as illustrated by the secretion of the mammary gland 

 where the output can be quantitatively tested. In starvation also the 

 general distribution of fat in the form of liposomes increases in many tis- 

 sues, particularly the glands a fact readily determined by studies of the 

 microscopic fat in fresh tissues. This phenomenon is not a fatty degenera- 

 tion as is sometimes held, it is only the redistribution of fat under the law 

 of reversible action of lipase to meet the emergency of tissue starvation. 



Lipogenesis. Noel Patton has shown a distinct accumulation of fat in 

 the liver of the frog in relation to fat feeding. For this phenomenon 

 Loevenhart has suggested the name lip agenesis. The idea is that the liver 

 in particular serves to a degree as a storehouse of fats, comparable to the 

 phenomenon of glycogenesis which characterizes the organ. The liver is 



